The cerebellum and its connections with other parts of the brain act as functional loops that underlie various aspects of motor control, learning, attention, language, working memory, and emotion. Disruption of these functional loops may be the basis for symptoms of schizophrenia, bipolar disorder, autism, fragile X syndrome, and other disorders. The current proposal is designed to examine sensory inputs to the cerebellum that are necessary for learning and to determine whether the cerebellum sends feedback to these sensory inputs during learning. Pavlovian eyeblink conditioning will be used as the method for assessing cerebellar learning. Previous findings from this project identified the neural pathway necessary for auditory eyeblink conditioning, which includes the medial auditory thalamus (MAT) and its projections to the pontine nuclei. MAT neurons exhibit learning-related changes in activity during eyeblink conditioning that are hypothesized to be driven by feedback from the cerebellum. The first aim of the current proposal is to identify the neural pathway(s) necessary for visual eyeblink conditioning and to determine whether the visual thalamus also shows learning-related activity using reversible inactivation and high-density neuronal recording methods. Aim 2 is to determine whether learning-related activity in the thalamus is driven by the cerebellum or its downstream target nuclei by recording neuronal activity in the thalamus while inactivating the cerebellum and its target nuclei. Aim 3 will investigate the mechanisms underlying cross-modal facilitation of cerebellar learning using high- density neuronal recording methods. Aim 4 is to determine the roles of auditory and visual areas of the cerebral cortex in cerebellar learning using reversible inactivation. The proposed project will significantly increase knowledge about the nature of cerebellar interactions with sensory areas of the brain that underlie associative learning. Findings from this project could be used to develop methods for treating various symptoms caused by pathology in cerebellar interactions with other brain areas.